Clamp devices for connecting members having cylindrical surfaces are known in a variety of configurations. For example, DE-OS No. 23 29 940, DE-GM No. 77 27 308 and DE No. 12 94 751 and DE No. 27 34 784 disclose such devices for connecting a cylindrical member to a shaft. These clamp devices may have simple layouts, i.e. with two conical rings arranged radially above each other and capable of being tightened against each other, or multiple configurations, wherein several conical rings are arranged radially above each other or axially in succession to each other, and actuated in this manner. A common feature of all of these is the fact that each clamp device comprises a separate part with a unitary cylindrical outer circumferential surface cooperating with the circumferential surface of a cylindrical bore, and a unitary cylindrical inner circumferential surface, seated on a shaft to be mounted within the bore. The clamp device is arranged in the space between the cylindrical outer circumferential surface of the shaft and the cylindrical inner circumferential surface of the bore. The two structural parts to be clamped, which may be rather large and heavy, do not need to have precise conical surfaces. The latter are present in the clamp set only, which acts outwardly through its cylindrical outer surfaces.
The transmittable torque depends on the frictional lock and thus on the radial stress produced by the clamp device between the inner and the outer structural parts. This stress is generated by the axial stressing force of straining screws connecting the parts of the clamp device. The axial force is converted by way of the conical surfaces into radial expansion of the clamp device. The mechanical strength of the straining screws yields an accurately determined maximum stress that may be applied by the clamp device in the radial direction. As, however, the stress is generated by axial displacement of the different conical rings over their conical or possibly cylindrical surfaces, frictional forces are generated and a significant portion of the existing total stressing force of the straining screws is lost to friction without being converted into a radial stress.
Even though the friction can be reduced by providing cleanly worked displacement surfaces and by oiling the surfaces with lubricants such as molybdenum disulfide, heretofore, there was always a certain metallic friction generated between the rings by the radial pressure. This friction results in correspondingly high losses of the stressing force of the screws during the axial displacement.